Public Health Warning Issued Related to Recent Sewage Discharge

BOSTON – JULY 22, 2023 – The following is a public health warning related to a recent sewage discharge, also known as a combined sewer overflow (CSO). State regulations require local public health departments to provide notice to the public when these discharges may create a risk to public health, including when a discharge lasts for more than two hours.  

Massachusetts Water Resources Authority Outflow MWR203, located in the Upper Inner Harbor, in Charlestown at the Charles River Dam upstream of North Washington St. Bridge, experienced a treated discharge or overflow starting on Friday, July 21 at 9:55pm pm creating a potential public health risk. This overflow ended at 2:56am on July 22 and this advisory will expire 48 hours after the overflow has ended. This event may potentially affect waters in Boston Inner Harbor.  

Several other discharges shorter than the two-hour threshold have also occurred. Note that these data are preliminary and may be revised. Check the Massachusetts Water Resources Authority website here and the Boston Water and Sewer Commission here for current updates.

The public is advised to avoid contact with affected water bodies for at least 48 hours after a sewage discharge or overflow, during rainstorms, and for 48 hours after rainstorms end, due to increased health risks from bacteria or other pollutants associated with urban stormwater runoff and discharges of untreated or partially treated wastewater.  

A combined sewer overflow occurs when a large storm overwhelms the combined sewerage system causing rainwater to mix with wastewater and discharge to a nearby water body. This prevents sewage backups into homes and businesses.  

More information about CSOs and public health is available at www.boston.gov/cso.   

 ###